UnboundLocalError: local variable 'epoch_logs' referenced before assignment

Traceback (most recent call last):
  File "pretrained_mlp.py", line 102, in <module>
    batch_size=1);
  File ".../keras/keras/models.py", line 465, in fit
    shuffle=shuffle, metrics=metrics)
  File ".../keras/keras/models.py", line 228, in _fit
    callbacks.on_epoch_end(epoch, epoch_logs)
UnboundLocalError: local variable 'epoch_logs' referenced before assignment

Has anybody ever had this issue? It infrequently comes up for me when training with autoencoders. I’m using python 2.7.8 on Ubuntu if that means anything.

[jeremykohn]

For me, the solution was a smaller batch size. Here’s why:

history = model.fit_generator(train_generator,
                              steps_per_epoch=nb_train_samples//batch_size,
                              ...
                              )

Since I mistakenly used a batch_size larger than the number of training samples, nb_train_samples//batch_size was rounded down to 0. And as @luis-i-reyes-castro explains, steps_per_epoch must be above 0.

[fchollet]

It can happen when the model is trained on empty data (which won’t work anyway). I can turn that into a clearer error message.